Question

已知A=4X平方-4XY+Y平方,B=X平方+XY-5Y平方

Answer 1

A=4X^2-4XY+Y^2,.(1)

B=X^2+XY-5Y^2.(2)

.(2)*4+,.(1)

A+4B=8X^2-19Y^2

8X^2-19Y^2=A+4B

4X^2-3XY=1,X^2-4Y^2=-3

A+B=4X^2-4XY+Y^2+X^2+XY-5Y^2

=5X^2-3XY-4Y^2

=(4X^2-3XY)+(X^2-4Y^2)

=1-3= -2